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In patent law, when one device contains substantially identical features of another device, is it said to “read on” that device. Buehler AG v. Ocrim S.p.A. Ocrim American, Inc., a Northern District of Texas case, offers a definition by describing that a device reads on a patented device when "the [reading on device] must employ means identical to or the equivalent of the structures, material, or acts described in the patent specification. The [reading on device] must also perform the identical function as [the patented device]."

A court may find that a device which reads on a patented device infringed that patent. Astra-Sjuco v. U.S. Intern. Trade Com’n, a U.S. Court of Customs and Patent Appeals case, lays out the two-step process that courts apply in adjudicating patent infringement claims: “[f]irst, the meaning of the claims in issue must be determined by a study of all relevant patent documents[;] [s]econd, the claims must be read on the accused structures.” That is, the allegedly infringing device must read on the existing patent to infringe by essentially being substantially identical. An example of a device which read on an existing patented device and therefore infringed in found in Fellowes, Inc. v. Michilin Prospecity Co., an Eastern District of Virginia case. There, the court found that paper shredders infringed a patent which referred to “spacer” that “consists of a V-shaped notch,” where the potentially infringing device had spacers, spaced apart cutting disks, circumferentially spaced teeth, and parallel cutting cylinders. The potentially infringing device read on the patent, the court held, because spacer could be separate from, or integral with, cutting disk as long as it was positioned between two adjacent cutting disks.

[Last updated in December of 2020 by the Wex Definitions Team]